Method for curing an organopolysiloxane using an organotin aminocarbamate

ABSTRACT

A HYDROXYL TERMINATED ORGANOPOLYSILOXANE IS CURED AT ROOM TEMPERATURE WITH AN ORGANOTIN AMINOCARBAMATE.

United States Patent Olfice 3,697,477 Patented Oct. 10, 1972 ABSTRACT OF THE DISCLOSURE A hydroxyl terminated organopolysiloxane is cured at room temperature with an organotin aminocarbamate.

This is a division of application Ser. No. 604,139, filed Dec. 23, 1966 now Pat. No. 3,520,910.

This invention relates to a new class of organotin compounds.

These compounds have been found particularly useful as catalysts in the room temperature curing of silicone rubbers derived from hydroxy-terminated methylpolysiloxane fluids. Theyare applicable also as intermediates and as catalysts in the preparation of methane foams.

A compound conforming to the invention may be considered an orgauo-substituted tin amioocarbamate wherein the tin atom is linked to the carbamic nitrogenatom, by which is meant the nitrogen atom corresponding to the nitrogen atom in carbamic acid (NH C'OOH). Alternatively, such a compound may be defined as a fully substituted stannane comprising one or both of the groups in which R is a hydrocarbon group, as alkyl or aryl.

In general, the compounds herein are embraced by the type formula 11 o R sn-N-h-o-Nx in which R is a hydrocarbon group, X is from the class =CRR and RR (where R again is a hydrocarbon group), and R is selected from the class consisting of hydrocarbon groups, oximo groups, diorganoaminooxy groups, the halogens, alkoxy groups, and

where R and X have the same significance as before indicated. For use as catalysts in the above-mentioned applications, the compounds preferred are those in which each of the Rs connected to the tin is a butyl radical and R is chlorine.

The compounds of the invention are for the most part condensation products of alkyl and aryl isocyanates with monoand bis-ketoximo and diorganoaminooxy stannanes:

msntonamon RNCO Such reactions are in general carried out to best advantage in the presence of a suitable hydrocarbon solvent as benzene, toluene, ligroin, and the like. The reactions proceed at room temperature, but higher temperatures may be employed to increase the reaction rate. In any case, anhydrous conditions should be maintained throughout the reaction.

The detailed practice of the invention is illustrated by the following examples which are not to be taken as in any way limitative thereof:

EXAMPLE I 7.43 g. of tributylacetoximostannane (BU3SDDN=CMCQ was dissolved in 30 ml. of ligroin in a vessel filled with nitrogen and equipped with a magnetic stirrer, addition funnel, reflux condenser and thermometer. Thereafter, an equimolar amount (2.44 g.) of phenylisocyannte, also dissolved in 30 ml. of ligroin, was added slowly over 25 minutes with stirring. A slight temperature rise was noted during the addition which was followed by a one-hour reflux period at a pot temperature of about C. The solvent was then removed in vacuo, leaving a viscous, pale-yellow residue, which was examined spectroscopically. The infra-red frequency characteristic of the N=C=O moiety had entirely disappeared with the development of an ester-type carbonyl frequency. Furthermore, the N.M.R. spectrum was in'compliance with the compound BmBnNO h ON=0Me in accordance with the reaction:

BmBnON=CMe| PhN=O=0 Bu:BnN-CO;N=OMB1 n EXAMPLEII An experiment .was performed in which only one oximo group on a dioximo-substituted tin compound was reacted, i.e.,

The apparatus was=as described in Example I, the order of addition," however, being reversed-a crucial factor. Thus, 3.97 g. (10.6 mmoles) of Bu,Sn(ON=CMe,,-), was

dissolvedin 30 ml. of ligroin and 1.29 g. (10.8 moles) of phenylisocyanate in 30ml. of ligroin. thereafter added with stirring. After solvent removal, no N=G=0 bond 7 was detectable in the infrared spectrum. The N.M.R. spectrum showed that one oximo group, Me @N -0--, was still attached to, the tin.

EXAMPLE H1 The above experiment was repeated, but instead of a 1:1 molar ratio of PhNCO to Bu,Sn(ON=CMe 2:1

ratio was used. This produced the fully substituted compound 0 Bu 0 Me1Gfl-O-gN- nN-tu0-N=Olde:

h' u h as shown by spectroscopic techniques.

EXAMPLE IV EXAMPLE VI The reaction:

rnsnwnunou=omsnmn zntNco was performed by adding a benzene solution of the tin compound (22.0 3., equivalent to 0.0605 mole) toa similar solution oi.ethyl.isocyanate (8.6 g., 0.121 mole). The reaction mixture was heated at 50 for one hour whereafter an infrared spectrum was taken of-the solution. The N=w frequencies had disappeared entirely. The N.M.R.

4. ketoximo hydrogens, indicating that these groups had been displaced from the tin atom, yielding as the product 0 P: 0 (Et) (Me) 0:14 O--N-An-N-(fl-O Bu 1 EXAMPLE VII A. hydroxy-terminated dimethylpolysiloxane fluid of 3520 cs. viscosity was intimately blended with a conventional cross-linker, commonly known as Ethyl Silicate 40, in a weight ratio of to 6. To this mixture one gram of thecompound prepared according to Example 111 was added with stirring. Elastomeric properties were evident in the product after 20 minutes air-exposure. A fully cured elastomer resulted in 45 minutes. The odor of the rubber was acceptable and the rubber did not have the corrosive properties often encountered with such rubhers when cured using conventional tin catalysts.

EXAMPLE VIII The procedure described in Example VII was repeated,

usingvonly 0.3 g. of catalyst per 100 g. of the hydroxyterminated polysiloxane mud. The cure-time was thus markedly slowed, three hours being required to obtain a fully cured rubber.

The two experiments demonstrate that with such a catalystthe cure-time becomes a function .of catalyst concentration. This is a desideratum, considering the variance in working periods to be met.

EXAMPLE IX All of the following were found to be active as curing agents for the rubber prepared as per Example VII:

BmBnNCPh) O OsN==OMe Isms n-N-OOaN -CMM Ma C=N l1 ams mtnuoom=omul BusSn-N(Ph) O 0sN=OMes Buss n ime oaoecml mnnooam (nuooakommemo 0:31.!

(Pine OIN=C (Me) a u, s n--N(E n c 0.N=o MEI EXAMPLE X Application of the tin compounds in the production of polyurethane foam: g. of a polypropylene glycol. is

spectrum showed shifts for the alkoxy and the 75 mixed with 9 g. of methylene chloride in ,a plastic-coated EXAMPLE XI A 50 ml., 3-necked flask was fitted with a magnetic stirrer, reflux condenser, addition funnel, thermometer, and nitrogen inlet. To the nitrogen-flushed apparatus were sequentially added with stirring 3.27 g. of phenylisocyanate in 15 ml. of ligroin and 5.61 g. of Bu Sn(ONEt in 15 ml. of the same solvent. A 6 C. temperature rise was noted. The molar ratio of the reactants was 2:1, so as to permit of the reaction:

BmSMONEU): 2PhNCO -r Bu:Sn(NCOiNEt After refluxing and vacuum stripping, the reaction was proved by infrared spectra, which showed the absence of any isocyanate bond and the presence of the characteristic carbonyl bond. The product compound when tested as per Example VII supra was found to be catalytically active.

EXAMPLE XII When EtNCO and Bu Sn(Cl)ONEt in 2:1 molar ratio were reacted in a manner similar to Example XI, one mole equivalent of ethylisocyanate was recovered, evidencing that the Sn-Cl moiety is inert under such conditions. The product BllSn-N-CO:N E t:

yields an excellent RTV silicone rubber when employed as a curing catalyst.

EXAMPLE XIII Addition of Bu,Sn(Me)ONEt; to an excess of phenylisocyanate yielded the compound N Ph) 0 01MB BuaSn (PhJC omen This compound showed activity as a polyurethane catalyst.

EXAMPLE XIV oNEtl BmSn ON=GMez was reacted in a 1:1 mole ratio with phenylisocyanate to obtain P11 BlhSn-IL-COzNEh N=CM6I For this result, it appears essential that the isocyanate be added slowly in dilute solution (e.g. toluene) to an equally dilute solution of the tin compound.

EXAMPLE XV The following compounds were prepared following the usual procedure:

Bu; SnN(Et) 0 ON Et,

Bu, SnN(Ph)C OzNEt:

NEta

Ph T L-C O NEh BuzSn N-C OzMe l st N--COgN=CMe BlhSn C0:NEt|

All were active as RTV silicone rubber curing catalysts, although the first-listed compound was less so that the others.

The invention claimed is:

1. A method for curing an organopolysiloxane composition to an elastomeric solid which comprises adding a compound of the formula wherein R is a hydrocarbon group, X is selected from the class consisting of =CRR and RR in which each R is a monovalent hydrocarbon radical and R is selected from the class consisting of hydrocarbon groups, oximo groups, diorganoaminooxy groups, the halogens, alkoxy groups and where R and X have the same significance as before indicated to a hydroxyl terminated organopolysiloxane containing a cross-linking agent.

References Cited UNITED STATES PATENTS 3/ 1967 Stamm 260429.7 7/1970 Lengnick et al. 260-429] DONALD E. CZAJA, Primary Examiner M. I. MARQUIS, Assistant Examiner US. Cl. X.R.

260-25 AC, 46.5 E, 429.7 

